Aircraft such as commercial airliners typically include control surfaces or devices mounted on the wings to improve the aerodynamic performance of the aircraft. Such control surfaces include wing leading edge devices and wing trailing edge devices and which may be deflected to improve the lift and/or drag characteristics of the wings. In addition, control surfaces such as miniature flaps may be mounted on the wing trailing edges and which may be deflected to increase the wing lift coefficient, alter the sectional pressure distribution, maintain airflow over the wing upper surface at high angles of attack, and other advantages. For example, miniature flaps may be deflected downwardly during cruise flight to increase the wing lift coefficient without significantly increasing aerodynamic drag which may improve the aerodynamic efficiency of the wings resulting in reduced fuel consumption and/or increased range. Miniature flaps may also maintain attachment of the airflow over the wing surface at high angles of attack which may reduce the aircraft stall speed.
Under certain flight conditions, it may be desirable to retract the miniature flaps from a deflected position back toward a neutral position. For example, for an aircraft encountering wind shear, it may be desirable to quickly retract the miniature flaps to avoid overloading the wing structure. For an aircraft moving at 500 to 600 miles per hour typical of cruise flight, it may be necessary to retract the miniature flaps in a relatively short period of time (e.g. within several seconds). It may also be desirable to deflect the miniature flaps upwardly during certain phases of flight to increase the aerodynamic performance of the wings. For example, upward deflection of the miniature flaps may improve the sectional lift characteristics of the wings.
One mechanism for actuating miniature flaps includes a shape memory alloy actuator. Unfortunately, shape memory alloy actuators are limited to deflecting flaps in a single direction, and rely on relatively slow cooling of the shape memory alloy material by ambient air to retract or move the miniature flaps in an opposite direction. In addition, shape memory alloy actuators have relatively slow actuation rates which may present challenges in quickly retracting the miniature flaps to prevent overloading the wings during certain flight conditions. Even further, shape memory alloy actuators have inherently low stiffness such that shape memory alloy actuators may be incapable of reacting aerodynamic loads on the miniature flaps. The inherently low stiffness of shape memory alloy actuators may lead to challenges in controlling flutter of the miniature flaps.
As can be seen, there exists a need in the art for a system and method of actuating miniature flaps which is capable of actuating such miniature flaps in opposite directions, is inherently stiff for reacting aerodynamic loads and minimizing flutter, and which allows for quick actuation and/or retraction of the miniature flaps.